Sum-capacity optimal spread-spectrum data hiding in video streams

We discuss mechanisms to hide multiuser data in a given host video stream with imperceptible spread-spectrum embedding. After constructing host vectors from original video stream, the hidden message for each user will be spread out with a signature and embedded to the host vectors. First, for any given total embedding distortion constraint, we give the optimal multi-signature assignment and amplitude allocation pair that maximizes the sum capacity of direct concealment procedure. Furthermore, if linear transformation of host vectors is allowed, we propose the transforming matrix design such that the embedded multiuser data lies in the orthogonal space of transformed host vectors.